Method of annealing and apparatus therefor



NW. A 25, 24. 1,516,645

Fiied Dec. 29. 1922 INVENTOR QMMWW so that the stee of New York and. State of Patented NovrZS, urrsn srArss PATENT orrlcn.

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Application filed heeember ae, 1928. Serial No. 809,659..

To all whom it may concern:

Be it known that I, Tuna GUs'rAr REN- NERFELT, citizen of the Kingdom of Sweden, and resident .of- New York cit invented certain new and useful Improve ments in Methods of Annealing and Apparatus Therefor, of which the following is a specification.

My invention relates to improvements in vfurnaces for heating, or for annealin metals, for instance steel. My improve furnace is particularly adapted ing cold rolled steel, heating it gradually'to a red heat and ermitting it to cool: slowly, will lose the, hardness acquired, by the cold rolling recess, and so that itwill retainits bright and spotless surface. {To gain this purpose my invention comprises means and apparatus to entirely pre'v ent,access of air or oxygen to the hot metal, and it is directed also to a new method of operating an annealing furnace for. such pur 'ose.

y invention is illustrated in the accom-.

panying drawing, in which Fig. 1 showsa vertical section of my improved furnace, Fig. 2 shows a cross section of the furnace, taken on line X-X of Fig. 1.

Referring to the drawing, 2

rep nts a muflleor crucible arranged to coiltain theobjects to be heated, and made of refractory material or, as shown on the drawing, of ironland thus able to withstand the shocks which will occur when the objects are sunk intoor' lifted from the mufie. Y The top pf the mufile is open, otherwise the mufie is airtight. 3 re resents a lid fastened to the top of the mufll a packing, for instance of asbestos, being interposed to make the joint fairly tight between lid and mufile. 4 represents a pipe leading from the bottom of the muflie, 5 another p1pe leading from the top, and 6 a small hole in the 11d, closed-by a screw. 7 represents a brickwall built around the mums and formed with an air space 8. The heat is generated in the annular space between the wall and the mums either by burning of gas, orv as shown in the drawing, by electric means. Three tubes 9, 9, 9 made of refractory material an'd'containin I ieces of coke "10 are arran aroun t 'e rnufie, the coke filling extending through the wall at llfforming terminals for connection to a, 3-phase electric power cir-v in the county. ew York, have a for anneal-.

tom of the tubes, throughwhich openings the coke fillings in the three tubes are electrically connected together. When the electric current is applied to the terminals 11 it will flow through the coke generate heat which is radiated to the mufie and its contents. 14 represents a windowv through which the glowing muflie may be observed. 15, 15 represent lids covering openings to the airspace and arranged to be opened more or less so as to regulate the coolin of the .furnace. '16 represents a removab roof, wasting on the wall. 17 represents a closed tank locatedat a lower level than the mufiie, arranged to contain keroseneor other suitablezliquid and connected with the muflle through the pipe 4.-- In this pipe connection 4; is a valve 18, agage 191and t e centrifugal pump 20 arran ed to pump liquid from the tankinto'st e muflle. 21 represents a tank or reservoir containing car bonic acid or other neutral gas and connected with the Inuflle through the pipe 5 for the purpose of filling the mufile with gas at a pressure slightly greater than atmospheric pressure. 22 represents a reducing valve which may be placed in the pipe connection 5 for regulating the pressure. 123 represents a valve, 24 a cooling device and 25 avessel containing a liquid hydrocarbon. 26 is a bent pipe of which one end extends into the vessel 25, its other end being connected to the pipe 5. A valve 27 is located in the pipe 26. v The method of operating the above described furnace is as follows:'The roof 16 and the lid 3 being removed, the objects to be annealed are lowered into mums for instance by means of chains. The objects may consist .of steel bars or steel stri s formed into coils or'may be of some ot er sha e. The lid 3 is placed on the muflle and tlg tened, the roof 16 is put place and valve 27 opened-the valve 23 bei closed beforehand. The valve 18 is o n and the pump started so that the liqui is drawn from the tank 17, creating a vacuum therein, and forced into the mufile so thatmost of the air contained within the mums is driven out fillings so as to through pipes 5 and 26. When the liquid will cause? such air as may be confined in crevices between the objects to expand and be dislodged by vapors from the liquid.

' vessel 25, and the valve 23 is opened. .Then

the valve 18 is opened so that the neutral gas will drive the liquid from pipes 26 and 5 and from the mufile'back into the tank 17.. When the gage 19 indicates that the pipe 4 is emptied .from liquid the valve 18 is closed. The space within the mufile, which is not occupied by the metal objects, is now filled with a neutral gas at sli htly greater than atmospheric pressure. he hydraulic seal formed by the oil in the vessel 25 prevents the gas from escaping throu h the pipe 26, and the loss of gas caused by eakage around the edge of the lid 3 is. small by reason of the small difference in pressure. Water is now turned on to the cooling device 24, and the heating of the furnace begins, by gas or electricity or coal, so that the muflle with its contents is slowly brought to a red heatj During this heating period the gas within the mufile will expand so that about two thirds of-the weight of the gas will escape through the liquid seal in 25. The temperature may be watched by means of pyrometers placed inside of the wall or by 0 -serving the muflle through the window 14.

Whenthe mufile is sufliciently heated, the firing of the furnace is stopped, and it is allowed to cool slowly. During the cooling period the same amount ofgas which escaped during theheating must be returned to the muffle. This amount is automatically supplied from the tank 21 and through the reducing valve 22, no part of it comin through the pipe 26 by reason of the liqui seal 25. The coolin of the furnace may be to some extent regu atedby the lids '15, 15.- When the furnace is sufliciently cold the roof and the lid 3 are removed the valve 23 is closed, and the objects lifted out of the mufile. They are now annealed, and since they were protected, while hot, from contact with any gas that could affect them their originalbr ght and spotless surface will be retained; 1

Many modifications can be made in the above described a paratus [and 'still fall within the scope o my claims. Some other liquid than kerosene can be used, for instance, gasolene, alcohol or ether. I can also use some other neutral gas than carbonic 861d for instance, nitrogen or common illuminating gas. The. hole 6 in' the lid may be omitted, and the amount of air remain ing in the muflle above the pipe 5 can be washed out by lowering the surface of the liquid in the muffle, in ecting gas from the pipe'5 and driving out the mixed gases by again raising the level of the liquid. The muflle may be made of rustfree steel, or it may be constructed of refractory material or formed integrally with the tubes 9 or with some parts thereof.

Having thus described my invention, what I claim is:

1. The method of annealing steel which consists in heating and, cooling the steel whileit is surrounded by a neutral gas at to contain metal objects, means "for filling it with'a liquid, means for replacing'the liquid by a gas, and means for heating the 4. The combination ofa mutlle arranged to be heated, means for filling it with a liquid, and means for replacing the liquid by a neutral gas at a pressure greater than atmospheric pressure. Y 5. The combination of a muffle, a tank at a lower level than the mufile arranged to contain a liquid, a pipe connection from the bottom of the mufile to the tank, a pump in the pipe connection, a reservoir arranged to contain a neutral gas, a pipe connection between the. muilile and the reservoir, and means for heating the mufile.

6. The combination of a mufile for annealing steel, means for removing; air from the muflle, means for filling it wit a neutral gas at greater than atmospheric pressure, and means for heating the muflle, together with means for causing a part of the gas to escape into the atmosphere during the heating period, means for cooling the mutlle, and, means for supplying gas to the muflle during. the cooling period.

7. The. combination of a muflle arranged to contain metal objects, means for creatso a pressure higher than atmospheric pressure, opening an exit into the atmosphere ing a vacuum in the mutflle, means for fill- U ing it with a gas, and means for heating it, together with automatically operating means for opening an exit into the atmos here for a part of the gas during the the muflie and the tank, a reservoir arranged to contain a neutral gas, a pipe connection between the muflie and the reservoir, a vessel, and a branch pipe extending from the last said pipe connection into the vessel; 7 9. The combination of a mufiie arranged to contain metal objects, a tank arranged to contain a liquid, .means for forcing liquid from the tank into the muflle, means for drawing the liquid from the muffle into vessel, and a branch pipe extending from vessel so as the pipe connection into the to form a seal.

12.'The combination of a'-mufile,'-'means for filling it with a neutral gas, a vessel arranged to contain a liquid, a pipe con-'- nection between the mufile and the vessel, and means for heating the muflle.

13. The combination of a muffie, means for creating 'a vacuum therein, means for filling it with a neutral gas, a vessel arranged to containa liquid, a pipe extending from the muflle into the vessel, means for heating the 'mufie, and means for cooling the pipe.

14. The combination of a mufie, means for filling it with a neutral gas, a vessel arranged to contain a ,liquid and to form a liquid seal, a pipe connection between the muffie, and,,the said seal, means for heating the muflie, and means, for cooling thepipe connection. i

15. The method of annealing metal within a muflle which consists in placing the metal in the mnfiie, creating a vacuum .in the. muflle, filling it with a neutral gas, heatingthe muflle and allowing it to cool.

16. The method of annealing metal withmetal in the mufl le, creating a vacuum in the muiflie, filling it with a neutral gas heating the mufie and expelling a part 0 the gas therefrom, cooling the mufie and supplyin an amount of gas thereto.

Signe at New York city, in the county of New York and State of New York, this in a mufile which consists in placing the 28th day of December, D.

TURE GUSTAF RENN-ERFELT.

Witness C. G. Nonns'rnom. 

